Bryan Caplan  

Dreaming the Simonian Dream

I Believe in Quantitative Easi... New Deal Panel, II...
Thought experiment: What would the world look like if every bit of land had the population density of Singapore?  With roughly 149 million square km of land on the planet, and a density of 6489 people per square km in Singapore, we get a world population of almost exactly one trillion.

What about a whole planet with the density of Manhattan?  That gets us to a little under 4 trillion souls.

If I have one complaint about the thought of Julian Simon, it's that he spent too much time insisting that supplies and long-run growth potential were "infinite."  These Zeno-style philosophical arguments are not necessary to sustain the radical but concrete hypothesis that in a few centuries, trillions of us might be prospering on planet Earth.  "It has to stop sometime" was as true when our population was 10,000 as it is today.  But as far as we can tell from the simultaneous rise of population and per-capita income, "sometime" is a long way off.

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COMMENTS (16 to date)
Brandon Berg writes:

The bottleneck isn't living space; it's food and energy production. Without radical advancements in these areas, it wouldn't be possible to populate the Earth fully at anywhere near those densities.

mtraven writes:

Imagine, an economist who isn't aware of the basic economic constraints of human existence. You get paid to teach economics, right? I suggest you find another line of work that doesn't involve committing fraud.

Justin writes:

It does not necessarily have to stop somewhere:

The land mass where terrestrial life lives is only a small percentage of the total livable space on earth with the oceans being so large. Plus, people can build up and out. If we run out of the resources to build up and out, we can borrow from other celestial bodies (without exotic loans, which will be gone by then, of course). We can start building vertical farms or setting up farm pipelines to other solar systems.

Hey, I can dream big, can't I?

peter jackson writes:

The world is a big place. I remember reading Thomas Sowell in the 80s positing that if you broke down the world's population at the time into hypothetical families of four and housed each in a standard working class suburban house and lot, we would all fit in Texas.

In his 1984 book "A Pattern for Failure," Sven Rydenfelt estimated that if the worldwide acreage under till at the time were all as productive as US farms, we could feed 40 billion people.


Blackadder writes:

The bottleneck isn't living space; it's food and energy production. Without radical advancements in these areas, it wouldn't be possible to populate the Earth fully at anywhere near those densities.

With hydroponics and nuclear energy, you probably could do this without using too much space. But suppose that we leave three quarters of land space for food and energy production. That still leaves you space for a trillion people at the population density of Manhattan.

And, as Simon noted, you could achieve a much higher livable population density in Manhattan just by repealing zoning regulations limiting the height of most buildings.

And, as Justin noted in the comments above, there's also a lot of space (either for food production or energy production or living) in the ocean or in outerspace.

Z. M. Davis writes:

In the Simonian long, long, long run, why even keep human bodies around? Just convert the Earth into computronium, and you probably have room enough for 10^30 human-equivalent minds.

floccina writes:

Great post and comments. Julian Simon is not appreciated enough.

24AheadDotCom writes:

What we could do is start going underground, just ignore the surface entirely and build entire cities deep beneath the earth. That way, our population would be infinite! Plus, in such a controlled environment it would be like a mall, 24/7, leaving even more time to engage in commerce. Let the dynamism begin!

(Note: that's sarcasm; I have to add this note because almost everything Caplan writes is indistinguishable from satire.) writes:

Mega-City One.

patri friedman writes:

Restricting yourself to the land surface of one planet? What a tiny world you live in, compared to the vastness of the universe.

Marcus writes:

"It has to stop sometime" was as true when our population was 10,000 as it is today.

Of course it is, it's always true. Yet that misses his point.

When the population was 10,000, where it has to stop was a lot lower number than it is today.

It'll stop when the cost of individuals exceeds the value of their benefits.

There's a lot of ways that can happen, like bad political systems with poor incentives.

Rick Beasley writes:

Not to get too far off the discussion thread, but is it not true that by having a birth rate that exceeds the death rate, we place externalities upon each other such as an increased demand for scarce goods?

Granted, advances in technology have kept up with (or enabled) much of our population's increased demand. But all things being equal, increased demand tends to increase prices. (Externality #1 - increased demand for scarce goods)

Additionally, because not all humans are born fully functional and most of us become less functional as we age, we pay the cost of caring for those additional people when our government decides that it is the humanitarian thing to do. (Externality #2 - increased cost of care)

I want to avoid making the assumption that individuals currently have no obligation to bear the costs of these externatilities placed on others (especially on future generations), but my hunch is that we don't really bear these costs - our children do.

Maybe more of an ethics discussion than an economical one. Thoughts?

Blackadder writes:


The line of reasoning you raise is actually dealt with extensively by Simon, particularly in the Ultimate Resource 2. Simon's argument, in brief, is as follows:

Greater consumption due to increase in population and growth of income heightens scarcity and induces price run-ups. A higher price represents an opportunity that leads inventors and businesspeople to seek new ways to satisfy the shortages. Some fail, at cost to themselves. A few succeed, and the final result is that we end up better off than if the original shortage problems had never arisen. That is, we need our problems, though this does not imply that we should purposely create additional problems for ourselves.

If you are like most people, your initial reaction to this argument is likely to be skepticism bordering on bafflement, as if someone had suggested that the cure for global warming was for people to breathe less. I would encourage you, though, to look into the matter and to try and do so as best as possible with an open mind. Many things that "everybody knows" about the effects of population growth turn out not to withstand scrutiny.

mtraven writes:

I don't believe I've ever seen a bigger, more steaming pile of innumerate crap than the proposition that the earth can support a population in the trillions. This is way beyond crackpot.

Humans at the current level of population use about 30% of the Earth's biological productivity. Where do you think the resources to support a 1000-fold increase in population are supposed to come from? Are we going to eat, drink, and breathe free-market magic? A population in the trillions would mean that the sheer mass of humans would be on the order of the total mass of all life in the present day (crops, forests, bacteria, and ocean life). The biomass to support all those humans -- where is it supposed to live?

Honestly, I always thought libertarians were pretty stupid but I did not realize they were this stupid.

gretnafc writes:


Think about it for a second:

When the earth's population was 10,000 you could've asked anyone if earth could support a hundred million and they would've thought you're on crack. And you can't blame them for thinking that: the way the world looked at that time, there was really no scope for having a hundred million around. But that's precisely the point: the way the world looks will inevitably change in unforseeable ways. When the earth had 10,000 people, they hadn't yet figured out agriculture, which led to a massive rise in population that couldn't have been foreseen until agriculture was foreseen, which happened precisely when agriculture was started.

Similarly, before the industrial revolution, no one could've imagined a world of 7 billions. But then the steam engine was invented and now we can easily make enough food to feed 10 billion without having to try too hard.

Looking from here on to a trillion people is unimaginable, but it is far less unimaginable than imagining 7 billion when earth had 10 million. And that actually happened.

But it probably won't matter anyway. We're probably going to nuke ourselves before we can ever worry about any of this, because most people are as short-sighted as you and will therefore continue to view impending disaster everywhere, bringing about stupid policies like protectionism, statism and socialism all the way till they bring about the real disasters.

mtraven writes:

The invalidity of that kind of argument by induction should be obvious to anybody with half a brain. Because technology has advanced and enabled population increase in the past is NO GUARANTEE AT ALL that it could do so in the future. Technology is not magic. It does not perform miracles if we only believe in it hard enough.

So yes, there MIGHT be some unimaginable change in technology that enables trillions of people to survive and thrive on the Earth. Maybe we will convert ourselves to software and live in integrated circuits. In that case, the surface area of the earth is not relevant. But if we are taking up physical space then we are taking up physical resources and there are not enough physical resources on the Earth to support that many people. Maybe nanotech and free energy will entirely remove humanity from biological necessity. It could happen! Lots of things could happen, that doesn't mean they are likely or that there is anything sensible to be said about such remote possibilities.

And because I am not willing to believe in miracles, then I'm responsible for statism and nuclear war. Right. Guess what -- we need to figure out how to not destroy ourselves while still retaining our biological nature.

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